There is a known method for producing hydrophilic polymer particles by reversed-phase suspension polymerization (see, for example, Patent Document 1). In particular, in producing hydrophilic polymer particles for use in, for example, cosmetic additives, carriers of various chemical substances, and surface modifiers for recording paper, it is important to control polymerization reaction of hydrophilic polymer particles in view of adjusting viscosity and feeling, for example, of a solution of polymer to be obtained.
Patent Document 2 discloses a method for producing polymer fine particles having a substantially uniform particle size in a specific range, specifically a method for producing high-concentration polymer slurry through reversed-phase suspension polymerization by supplying a water-soluble oxidizer and a water-soluble reducer as polymerization initiators to a vinyl monomer aqueous solution and adding a monomer aqueous solution to the obtained slurry for further polymerization. Patent Document 2 also describes a method for deactivating a catalyst with an oxygen-containing gas in order to avoid the influence of a remaining unreacted polymerization catalyst when the polymerization reaction is terminated.
Patent Document 3 shows a method for producing polymerized toner in order to suppress occurrence of odor due to a remaining or liberated chain transfer agent, specifically a method of bubbling a carrier gas in a reaction solution.
Patent Document 4 describes a method for producing toner in which attachment of polymer to a wall surface of a reaction vessel is prevented by introducing a carrier gas into a gas-phase portion of the reaction vessel.